As used herein, the term "isoflavone forms" includes malonyl, acetyl, glucoside, and aglycone forms of the isoflavones.
This invention will find use when processing any one of a number of plants or plant material, the preferred one of which is the soybean.
Those who are skilled in the art will readily perceive a variety of other plants or plant material which may be used, for example, kudzu and subterranean clover are also expected to work in this invention. Accordingly, the terms plant, plant material, and vegetable are to be construed herein as including these and other suitable materials.
For some background information on processing soy, reference may be made to the following articles: "Isolated Soy Protein" by C. W. Kolar, S. H. Richert, C. D. Decker, F. H. Steinke, and R. J. VanderZanden, found as chapter VIII of New Protein Foods, Vo. 5, eds. Aaron M. Altschul and Harold L. Wilcke, Academic Press, Inc. 1985; "Traditional Soyfoods: Processing and Production" by Peter Goldbitz; and "Soy Protein Products; Processing and Use" by Edmund W. Lucas and Mian N. Raz, both (0022-3166/95) published 1995 by the American Institute of Nutrition. A process for producing soy whey is disclosed on pages 386, 387 of "Soybeans Chemistry, Technology, and Utilization" by KeShun Liu, published by Chapman & Hall, 115 Fifth Avenue, New York, N.Y. 10003.
Isoflavones are a unique class of plant flavonoids that have a limited distribution in the plant kingdom and may be physically described as colorless, crystalline ketones. The most common and important dietary source of these isoflavones are soybeans which contain the following twelve isoflavone isomers: genistein, genistin, 6"-0-malonylgenistin, 6"-0-acetylgenistin, daidzein, daidzein, 6"-0-malonyldaidzein, 6"-0-acetylgenistin; glycitein, glycitin, 6"-0-malonylglycitin, 6"-0-acetylglycitin (Kudou, Agric. Biol. Chem. 1991, 55, 2227-2233). Ninety-seven to ninety-eight percent of the soybean isoflavones are in the glycosylated form.
Traditionally, individuals have been limited in their use of soy foods to increase their levels of dietary isoflavones because the number and variety of soy foods available in the U.S. marketplace is limited. Also, natural flavors and color of some soy products have been described as bitter and unappetizing.
The isoflavone, genistin, was first isolated from soybean meal in 1931 by Walz (Justus Liebigs Ann. Chem 489, 118) and later confirmed in 1941 by Walter (J. Amer. Chem. Soc. 63, 3273). Patents have described the production of isoflavone enriched soy-protein products (WO 95/10512, WO 95/10529; WO 95/10530), genistin malonate and daidzen malonate (U.S. Pat. No. 5,141,746), pharmaceutical-type compositions containing isoflavones (U.S. Pat. Nos. 5,424,331; 4,883,788), and isolation and modification of isoflavones from tempeh (U.S. Pat. Nos. 4,390,559; 4,366,248; 4,366,082; 4,264,509; 4,232,122; 4,157,984). The present patent relates to the manufacture of highly enriched isoflavone products containing either a wide-range of soy isoflavones or highly-purified genistin gained from an ethanol extract of defatted soybean flakes.
Coronary heart disease (CHD) is a leading cause of death, especially in the United States and other industrialized nations. Elevated total and low density lipoprotein (LDL) cholesterol levels are important risk factors for CHD. In humans, soy protein products appear to lower serum total cholesterol levels by an average of about 9.3% and to lower low-density lipoprotein (LDL) cholesterol by an average of about 12.9% when consumed at an average intake level of 47 g soy protein per day (Anderson et al., NEJM, 333: 276-282, 1995).
Isoflavones (Phytoestrogens) are implicated as a class of compounds in soy protein products which is at least partly responsible for this cholesterol-lowering effect in animals (Setchell, in McLachlan JA, ed. Estrogens in the Environment II: 69-85, 1985). In addition, studies with primates suggest that soy isoflavones may account for up to about 60-70% of the hypochoesterolemic properties of soy protein (Anthony et al., Circulation, 90: Suppl: I-235 (abstract), 1994; Anthony et al., J. Nutr., 125: Suppl 3S: 803S-804S (abstract), 1995; Anthony et al., Circulation, 91: 925 (abstract), 1995).
It has also been suggested that isoflavones have an ability to play a role in the prevention of certain cancers. Japanese women who have consumed diets rich in isoflavones appear to have a very low incidence of breast cancer (Adlercreutz et al., J. Nutr. 125: 757S-770S, 1995). Soy products have also been shown to decrease mammary tumor formation or to inhibit mammary tumor progression in rat breast cancer models (Barnes et al., Clin. Biol. Res. 347: 239-253; Hawrylewicz et al., J. Nutr. 121: 1693-1698, 1991). Genistein has been shown to inhibit protein tyrosine kinase (Akiyama et al., J. Biol. Chem. 262: 5592-5595, 1987), to inhibit angiogenesis (Fotsis et al., Proc. Natl. Acad. Sci. USA 90: 2690-2694, 1993), and to induce differentiation in several malignant cell lines (Peterson, J. Nutr. 125: 784S-789S, 1995), all of which may be important risk factors in cancer development. Genistein and Biochanin A also appear to inhibit the growth of androgen-dependent and independent prostatic cancer cells in vitro (Peterson and Barnes, Prostate 22: 335-345, 1993). Genistein may act as an antioxidant (Wei et al., Nutr. Cancer 20: 1-12, 1993).
Beyond cancer, it is thought that at least some of the soy isoflavone fractions were especially beneficial for women in general since it is a source of plant estrogen. It is thought that plant estrogen provides many of the advantages and avoids some of the alleged disadvantages of animal estrogen. Hence, it is especially desirable to enable the isoflavone fractions to be used in a wide variety of ways, such as in beverages and foods. This means that the isoflavone fractions should not introduce unacceptable tastes or unappetizing colors.
The process described in the above-cited U.S. Pat. No. 5,702,752 produces an excellent concentration of isoflavones. However, the end product could be improved because it had a color and flavor which sometimes tended to limit its desirability. For example, there has been a tendency to think that soy isoflavone fractions should be limited to uses where the consumer does not either taste or really see it, as when the isoflavones are formed into tablets, pills, or capsules.
There are other uses for isoflavones which are desired. For example, there are times when it is desirable to use the isoflavones in foods, beverages, medical foods, and certain dietary supplement products.